Apparatus for epitaxial growth from the liquid state

ABSTRACT

Means effect epitaxial growth from the liquid state. A crucible is supported within and co-caxially with an inclined, cylindrical furnace tube. An annular holder, aligned and operatively associated with the crucible supports a substrate-clamp means within the crucible and offset from the common axis of the tube, crucible and holder. Rotation of the holder carries the substrate into, through and out of a pool of the liquid contained in the crucible.

United States Patent Kobayasi Sept. 2, 1975 APPARATUS FOR EPITAXIALGROWI'H [56] References Cited FROM THE LIQUID STATE UNITED STATESPATENTS (75] Inventor: Hiroyuki Kobayasi, Kadoma, Japan 3,558,373 I/l97lMoody et a! I4S/l7l [73] Assignee: Matsushita Electric Industrial Co.,FOREIGN PATENTS OR APPLICATIONS -J p 754,767 8/1956 United KingdomI48/l72 [22] Filed: Oct. 31,1974

Primary ExaminerMorris Kaplan 1 PP N05 5l9-744 Attorney, Agent, orFirm-Depaoli & OBrien Related US. Application Data [60] Division of $61.No. 463.406, April 23, 1974, Pat. [57] ABSTRACT No. 3,858,55l, which isa division of Ser. No. Means effect epitaxial growth from the liquidstate, A 262.529.J n I4. I 7 Pat. which is crucible is supported withinand co-caxially with an a continuation of S N 860,772, Sept. 24, Iinclined, cylindrical Furnace tube. An annular holder abandoned alignedand operatively associated with the crucible supports a substrate-clampmeans within the crucible [52] 118/426 and offset from the common axisof the tube, crucible [5H BOSC 3/09 and holder. Rotation of the holdercarries the sub- [58] Field of Search I 18/421, 426, 429, 423,

118/503; [48/171, I72; II7/20l, [I4 A, I14 B, II4C, 114R, ll3

strate into, through and out of a pool of the liquid contained in thecrucible.

1 Claim, ll Drawing Figures sum 1 BF 4 PRIOR ART 1 PATENTED EP 2197ssnanenrg APPARATUS FOR EPITAXIAL GROWTH FROM THE LIQUID STATE This is adivision of application Ser. No. 463,406. filed Apr. 23, 1974, now Pat.No. 3,858,551, which is a division of application Ser. No. 262,529,filed June 14, I972, now U.S. Pat. No. 3.827399, which in turn is acontinuation of application Ser. No. 860.772, filed Sept. 24, 1969, nowabandoned.

This invention relates to improved apparatus for epitaxial growth fromthe liquid state.

It is an object of this invention to provide an apparatus used forliquid-phase epitaxy which apparatus is simple in construction.

It is another object of this invention to provide an apparatus adaptedfor the purpose and having a shorter constant-temperature zone than insuch apparatus as has been available heretofore.

It is another object of this invention to provide an apparatus which iscapable of multi-layer epitaxial growth.

These and other objects will be effected by this invention as will beapparent from the following description taken in accordance with theaccompanying drawings, in which:

FIG. I is a longitudinal section ofa conventional apparatus forepitaxial growth from the liquid state.

FIG. 2 is a view similar to FIG. 1, showing an appara tus for epitaxialgrowth from the liquid state constructed in accordance with a firstembodiment of this invention.

FIG. 3 is a cross section on the line II of FIG. 2.

FIG. 4 is a partially cut away top plan view showing a second embodimentof this invention.

FIG. 5 is a view similar to FIG. 3, showing the apparatus of FIG. 4 astaken along the line [III of FIG. 4.

FIG. 6 is a longitudinal section as taken along the line III-Ill of FIG.4.

FIGS, 7 and 8 are longitudinal sections ofa third embodiment of thisinvention in different relative positions.

FIG. 9 is a longitudinal section of an apparatus according to a fourthembodiment of this invention.

FIG. 10 shows schematically a cylindrical crucible incorporated in theapparatus of FIG. 9.

FIG. 11 shows schematically a cylindrical member for supporting thesubstrate wafer, which is incorporated in the apparatus of FIG. 9.

FIG. 1 shows a conventional apparatus 10 used for liquid-phase epitaxy.The apparatus as shown comprises, largely, a furnace tube 11 made of,for example, quartz, a heating coil 12 surrounding the furnace tube 11,and a boat 13 provided internally of the furnace tube 11 and made of,for example, graphite, glassy carbon or quartz. In the diagram, thestarting condition for the epitaxial growth from the liquid state isillustrated. As illustrated, the apparatus 10 is tipped and a substratewafer 14 to be processed is held tightly against the upper end of theflat bottom of the boat 13. At the lower end of the boat is placed amixture of a material 15 to be epitaxially grown on the substrate wafer14 and a solvent 16 therefor. The boat 13 is held in positionsubstantially at the middle portion of a constanttemperature zone of thefurnace tube 1], which zone results from the heating coil 12. With thefurnace tube 11 tipped as shown and with a flow of alternate gas throughthe tube 11, the boat 13 is heated to a predetermined temperature. Asthe temperature rises, the material 15 dissolves in the solvent 16 atthe lower end of the boat 13. When the temperature reaches thepredetermined temperature, the solvent I6 is saturated with the material15. At this time, the furnace tube 11 is tipped so that the moltenmaterial covers the exposed surface of the substrate wafer 14, and theheating power is turned off. As the furnace cools down, precipitation ofthe material from the solution and epitaxial growth upon the substrate14 occur.

The apparatus 10 of this known type, however, has the disadvantages thatit requires not only a complicated mechanism for swinging the furnaceabout an axis perpendicular to the tube axis but also a long furnace forforming a relatively long constant-temperature zone. Furthermore, it isdifficult to maintain the zone at desired temperatures before and afterthe swinging operations.

Such difficulties are eliminated in the apparatus for epitaxial growthfrom the liquid state of this invention. Referring to FIG. 2, alongitudinal section of the present apparatus 17 according to a firstembodiment of this invention is shown. The apparatus 17 comprises, ascustomary, a furnace tube 18, a heating coil 19 surrounding the furnacetube 18 and a boat 20 provided internally of the tube 18. The boat 20used in this em' bodiment is, as shown in FIG. 3, different inconstruction from that of FIG. 1 in that before the epitaxial growth asubstrate wafer 21 is isolated from a solution 22 in cross section, notaxially. The boat 20 is generally semi-cylindrical, having a firstaxially extending sunk portion 23 for storing the solution 22 containinga material 24 to be epitaxially grown on the substrate wafer 21, asecond axially extending sunk portion 25 for holding the substrate wafer21 and an axially extending raised portion 26 isolating in cross sectionthe first sunk portion 22 from the second 25. Similarly to FIG. I, thesubstrate wafer 21 is fixed tightly against the bottom of the secondsunk portion 25 by means of a clamping member 27.

In operation, the boat 20 is rotated clockwise about its axis so thatthe solution 22 stored in the first sunk portion 23 flows into thesecond sunk portion 25 and covers the exposed surface of the substratedwafer 21. With this arrangement, the constant-temperature zone necessaryfor the uniform heating of the substrate wafer 21 and the solution 22 isshorter than that of the conventional apparatus in which the substratewafer is isolated from the solution in the axial direction. Furthermore,an increased efficiency of processing is achieved with a limited lengthof the constanttemperature zone, because a number of substrate waferscan be juxtaposed along the length of the zone. Still furthermore, thisarrangement is simpler in construction than the conventional one becauseit is unnecessary to have the entire furnace tipped about the axisperpendicular to the tube axis.

FIGS. 4, 5 and 6 show a second embodiment of this invention which iscapable of multi-layer epitaxial growth. As best seen in FIGS. 4 and 5,the boat 28 as used is similar in construction to the boat 20 of FIG. 3in that it has a first sunk portion 29 for storing a first solution 30containing a first material 31 to be epitaxially grown, a second sunkportion 32 for holding a substrate wafer 33 and a first raised portion34 isolating in cross section the first sunk portion 29 from the second32. In addition to these portions 29, 32, 34, the boat 28 is providedwith a third sunk portion 35 for storing a second solution 36 containinga second material 37 to be epitaxially grown on the substrate wafer 33and a second raised portion 38 isolating axially the second sunk portion32 from the third 35, as is clearly shown in FIG. 6.

In operation, the boat 28 is first rotated clockwise about the axis ofthe furnace tube 39 while kept in its axially horizontal position sothat the first solution 30 flows into the exposed surface of thesubstrate wafer 33 to cause a first epitaxial layer to be formed on thesubstrate wafer 33. The boat 28 is then rotated counterclockwise aboutthe tube axis until it resumes its original position shown in FIG. 5.The furnace tube 39 is thereafter tipped about an axis perpendicular tothe tube axis counterclockwise as seen in FIG. 6, so that the secondsolution 36 stored in the third sunk portion 35 flows into the secondsunk portion 32 to cover the surface of the substrate wafer 33. Thus, asecond epitaxial layer is formed on the first epitaxial layer previouslyformed on the substrate wafer 33.

With the arrangement as proposed, it is possible to have a plurality ofepitaxial layers formed on a substrate wafer.

FIGS. 7 and 8 show a third embodiment of this invention. As shown, thefurnace tube 40 is kept tipped during the operation. Internally of thefurnace tube 40 is provided a cylindrical crucible 41 for storing asolution 42 containing a material 43 to be epitaxially grown on asubstrate wafer 44. To prevent the crucible 41 from slipping downthrough the tube 40, a constriction 45 is provided in the furnace tube40. Adjacent the end of the crucible 41 opposite to the constriction 45is provided a cylindrical member 46 for supporting the substrate 44. Thesubstrate 44 is suspended above the solution 42 by a suitable means 47.The means 47 comprises a first plate member 48 made of the same materialas that of the cylindrical crucible 41, for example, ceramics, and asecond plate member 49 for clamping the substrate wafer 44 onto thefirst plate member 48. The second plate member 49 may also be made ofthe same material as that of the cylindrical crucible 41. The first andsecond plate members 48, 49 are attached at their one ends to thecylindrical member 46 by suitable adhesives. However, where these platemembers 48, 49 are made of such material as cannot be adhered to thecylindrical member 46, they may be attached to supporting members (notshown) which are anchored to the cylindrical member 46.

In operation, the substrate wafer 44 suspended above the solution 42 bythe clamping means 47 is immersed in the solution 42 by swinging thecylindrical member 46 about its axis, as is clearly shown in FIG. 8. Byso doing, an epitaxial film is grown on the substrate wafer 44. With thearrangement as proposed, the required constant-temperature zone issignificantly shortened. providing simplicity of the entireconstruction. Furthermore, the substrate wafer 44 which is supported notby the crucible 41 but by the cylindrical member 46 is easily accessiblefrom outside furnace tube 40.

FIG. 9 shows another embodiment of this invention which is similar tothat of FIG. 7 in that the container (which actually is an alternativeof the boat used in the preceding embodiments) for the solution and themember for supporting the substrate wafer are structurally isolated fromeach other. The apparatus 50 as shown, largely, comprises a generallycylindrical casing 51, a

cylindrical crucible 52 for storing a solution 53 containing a material54 to be epitaxially grown on the sub strate wafer 55, said crucible 52being provided internally of the casing 51, a cylindrical member 56 forsupporting the substrate 55, said cylindrical member 56 being alsoprovided internally of the casing 51 and a furnace tube 57 having aheating coil (not shown) pro vided therearound and having the casing 51accommodated therein. The casing 51 is provided at one end with a smallport 58 for substituting a gas. The cylindrical crucible 52 is, as isclearly shown in FIG. 10, of a cylindrical configuration having a smallcircular port 59, 60 formed centrally in each side wall thereof. Theoutside diameter of this cylindrical crucible 52 is slightly smallerthan the inside diameter of the casing 51. The cylindrical member 56 hasan outside diameter equal to that of the cylindrical crucible 52.

As is clearly shown in FIG. 11, a supporting member 61 is provideddiametrically of the cylindrical member 56 for carrying clamping means62. The clamping means 62 comprises a stepped plate-like member 63 and aspring member 64 attached thereto and serves to clamp the substratewafer 55 and suspend it in the cylindrical crucible 52 above thesolution 53 off the axis thereof.

A cap member 65 having two openings is provided in the furnace tube 57.One of the openings 66, which is positioned in alignment with the tubeaxis, hermetically receives a shaft 67 for rotating the cylindricalmember 56. The other of the openings 68 is provided for feedingalternate gas into the furnace tube 57. The shaft 67 is linked to ajoint 69 which is secured to the supporting member 61 diametricallymounted on the cylindrical member 56. Thus, when the cylindrical member56 is rotated about its axis in the casing 51 by rotating the shaft 67,the substrate wafer 55 secured to the clamping means 62 is immersed inthe solution 53 stored in the cylindrical crucible 52.

It is to be noted that the components of the apparatus should be made ofsuch materials as having a stability in high temperature conditions.These materials include quartz, graphite and glassy carbon. It will nowbe appreciated that, with the arrangements as herein described andshown, the constant-temperature zone necessary for uniformly heating thesubstrate wafer and the solution can be shortened compared with that ofthe conventional apparatus.

What is claimed is:

1. Apparatus for epitaxial growth of a film on a substrate from theliquid state comprising:

A cylindrical furnace tube disposed on an incline;

an annular shoulder extending from the internal wall of said tube;

a heating coil surrounding a portion of said tube;

a crucible, coaxial with said tube, supported on said shoulder anddisposed within said surrounded portion and containing a pool of saidliquid;

an annular holder, coaxial with said tube and disposed therewithin abovesaid crucible and in substantial alignment with the crucible side wall;and

substrate-clamp means supported on and generally closely spaced from,the internal wall of said holder and extending axially thereof so as tolocate a said substrate within said crucible and offset from the commonaxis of said inclined tube, crucible and bolder;

whereby on rotation of said holder said substrate may be carried into,through and out of said pool to effect the epitaxial growth.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 902,454 Dated September 2 1975 Inventor s) H Kobayasi It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

[30] Foreign Application Priority Data September 27, 1968 Japan.43-70902 ,jigned and Scaled this [SEAL] twemy'nimh r June 1976 A nest:

RUTH C. M Arrestin 05:3 MARsHALL DANN Commissioner ufP and Trademarks

1. Apparatus for epitaxial growth of a film on a substrate from theliquid state comprising: A cylindrical furnace tube disposed on anincline; an annular shoulder extending from the internal wall of saidtube; a heating coil surrounding a portion of said tube; a crucible,coaxial with said tube, supported on said shoulder and disposed withinsaid surrounded portion and containing a pool of said liquid; an annularholder, coaxial with said tube and disposed therewithin above saidcrucible and in substantial alignment with the crucible side wall; andsubstrate-clamp means supported on and generally closely spaced from,the internal wall of said holder and extending axially thereof so as tolocate a said substrate within said crucible and offset from the commonaxis of said inclined tube, crucible and holder; whereby on rotation ofsaid holder said substrate may be carried into, through and out of saidpool to effect the epitaxial growth.